Conventional lamp socket devices in Christmas lighting strings have a lamp bulb, lamp base, lamp holder and contact copper sheet connected to the electrical wires. In general different specifications of lamp bulb are not used. The lamp bulb is only used in certain conditions or situations. Further, a lighting string used in series or parallel does not have any limit or control. Only words in a label or a written explanation warning is provided on such strings as sold. Thus, users may neglect to heed such explanations. This can present the danger of over heating, something catching fire, etc. due to the improper use. Therefore, a fire disaster may occur, potentially causing great loss in life and property.
The use a bulbs with a screw base in the lamp socket device is based on one type, such as with 1OW, 2OW . . . 20OW bulbs used in households appliances. The same to use E 26 base and holder. It should be limited to use in various situations. However, only explanation or warning is done. It has not any effective method or design to protect the users to assembly or replace the device without error whereby to guarantee the safety.
Several decades, a number of lighting strings in series or parallel have different specifications of lamp bulbs (1), which is to use the same specification of lamp base (2) or lamp holder (3). This only relies on the control of manufacture and a written explanation or warning in order to prevent the users from improper use. Especially, the consumers are not familiar and cannot recognize products and distinguish the specifications, i.e. it is difficult to apply common sense to them. Thus, a disaster can result due to neglect. The conventional products use different lamp bulbs (1), use the same specification of lamp base (2) or lamp holder (3), such as in the prior arts of U.S. Pat. Nos. 3,286,008; 4,631,650; 4,679,126; 4,779,177; 4,807,098; 4,970,632; 4,999,751; 5,001,615; 5,193,255 and 5,418,698. Though the combination of lamp bulb, lamp base or lamp holder has a limit in vertical or horizontal direction, the purpose is, under the combination, to make the conductor wire of bulb only able to contact with the electric wire or contact the copper sheet so as to complete the electrical circuit.